The invention relates to an electric motor having a flange disk that is arranged vertically to the motor shaft, and the stator being fixed to the interior side of said flange disk, and having a control circuit for the motor for which a circuit board is provided that is arranged plane-parallel to the flange disk on the side of the stator that faces the flange disk.
In the case of an electric motor of this type that is known from DE-Al No. 25 14 067, the circuit board is developed to be ring-shaped and is arranged coaxially to the motor shaft between the stator and the flange disk.
For the mass production of driving motors, an electric circuit is required that, as a rule, is manufactured at a separate manufacturing site. Those manufacturers of electric motors who are not equipped for manufacturing circuits of this type, purchase these, together with the circuit board, from the outside. Large-scale purchasers of electric motors of this type are often manufacturers of electronic apparatuses. Under certain circumstances, these large-scale purchasers may be able to cost-effectively manufacture these circuits with the circuit boards themselves. This is particularly true if the electric motors in question are part of a fan, for such fans are often used for the cooling in electronic apparatuses.
For this reason, it is an objective of the invention to develop an electric motor of the initially mentioned type in such a way that the circuit board with the circuit can subsequently be conveniently installed into the otherwise completely finished electric motor, for the purpose of rationalizing the manufacturing process, in that, for example, the manufacturer of electric motors furnishes the electric motors to his customers without the circuit board, and the customer can then manufacture the circuit boards rationally himself and can also install them subsequently in a convenient way.
An objective is achieved by the fact that the circuit board is arranged on the exterior side of the flange disk that faces away from the stator.
For this purpose, the circuit board is preferably ring-shaped--possibly with recesses at the exterior edge--and arranged coaxially to the motor shaft.
The invention makes it possible to prefabricate unfinished driving motors that are fully operable finished driving motors, except for the circuit board that has to be inserted, and then subsequently, when required, equip them with a circuit board and as a result finish them completely.
Circuit boards may be used that are equipped with different control circuits, according to the desired motor operation. In this case, only one single unfinished motor type must be held available for different types of motors, which simplifies mass production and also warehousing.
The circuit boards may be glued in, clamped in, screwed in or fastened in another way. It is advantageous to fasten the circuit board by means of a locking means into which the circuit board can be easily inserted. On such a locking arrangement, a passageway is provided through the circuit board and spring elements on the flange disk are compressed together and inserted through the passageway and then allowed to expand and catch onto recess areas on the circuit board, to hold the circuit board to the flange disk. In this way, the subsequent mounting of the circuit board is largely prepared and facilitated.
The connection of the stator to the circuit board may take place by soldered or welded electrical connections. The required soldering and welding operations are not necessary if the connection is established by means of contacts connected to the stator which automatically cooperate with counter-contacts on the circuit board when the board is inserted into the flange disk.
It is recommended to cover the circuit board on its back side facing away from the flange disk by means of an insulating plate. The insulating plate may be a glued-on foil.
The circuit board is held securely and also protected with respect to mechanical outside effects if a recess is provided on the exterior side of the flange disk, into which the circuit board fits. In this case, the fit can exist only in the case of a certain rotating position of the circuit board and always ensure the same assembly situation.
It is desirable that the circuit board not protrude to the outside from the contour of the flange disk and thus not increase the axial length of the electric motor. This can be achieved by a correspondingly flat development of the circuit board and a deep development of the indentation.
Under certain circumstances, built-up circuit elements are used in the control circuit. These are preferably arranged on the front side of the circuit board that faces the flange disk, and if they do not find space in the identation, they will find space in the provided recesses and/or breakthroughs of the flange disk.
The magnetic field change-over in response to the revolution timing of an electric motor, in the case of modern motors of the type that is concerned here, preferably takes place by a contactless scanning of the respective rotational position of the rotor. A sensor element that is required for this purpose, for its function, must have a certain position in proximity of the rotor.
The invention can preferably be used in motors that are equipped with this type of sensor element, because, by means of the invention, it can be ensured in a simple way that the sensor element, when the circuit board is inserted, always takes up precisely the position that is indicated for its function. To that end, the sensor element is mounted to the circuit board at its exterior side and extends through an aperature therein toward the rotor so that when the circuit board is positioned securely in its recess in the flange disk, the sensor is extended through the aperture adjacent the rotor. Since the circuit board can only be located in one position on the flange disk, the sensor is always positioned accurately.
In such a case, the development as a collectorless direct-current motor having a permanent-magnetic external rotor is preferred.
The sensor element may be a Hall generator. Preferably this Hall generator will be combined with the pertaining amplifier to form one single, integrated control element. This type of Hall generator, when the circuit board is inserted, projects close to the rotor poles, while leaving an air gap.
Advantageously, the circuit board can be inserted into the otherwise completely mounted unfinished motor in such a way that the unfinished motor, when the circuit board is inserted and connected and when, if required, the insulating disk is placed on it, is finished and operable. In this way, the motor is prefabricated except for the circuit board and its connection. The subsequent completion by equipping with the circuit board requires only minimal expenditures.
A preferred use of the invention is in connection with a fan driven by a small electric motor, because fans of this type, in large numbers, are installed into eletronic and electrical apparatuses for the purpose of cooling them. The manufacturers of these electrical apparatuses who buy these fans from the outside from other manufacturing specialists, are well equipped for manufacturing electrical circuit boards and can particularly utilize the capacity for later installing the circuit board provided by means of the invention. In this case the circumstance also has an effect that this circuit board must be connected to the circuit of the electronic apparatus, so that the connecting process for the connection of the circuit board to the unfinished motor is compatible with manufacturing of the apparatuses.
Electric motors of the type that is concerned here, as a rule, are tested with respect to their operation. This type of test is also desirable for the unfinished motors, if these are furnished for being later equipped with the circuit board. A manufacturing process that permits this type of testing of the unfinished motors in a simple way is obtained by having the motor complete except for the circuit board so that it can be tested and shipped. At the shipped to site, the circuit board is added without disassembly of any of the motor portions to render a complete motor unit. Therefore full testing of the motor and pump can occur at the factory.